"Twenty-six scientists from 10
countries evaluated the available evidence on the
carcinogenicity of formaldehyde, a widely used chemical",
reports Dr Peter Boyle, Director of the International Agency for
Research on Cancer (IARC), part of the World Health Organization.
The working group, convened by the IARC Monographs
Programme, concluded that formaldehyde is carcinogenic to
humans. Previous evaluations, based on the smaller number of
studies available at that time, had concluded that formaldehyde
was probably carcinogenic to humans, but new information
from studies of persons exposed to formaldehyde has increased
the overall weight of the evidence.

Based on this new information, the
expert working group has determined that there is now
sufficient evidence that formaldehyde causes nasopharyngeal
cancer in humans, a rare cancer in developed countries. "Their
conclusion that there is adequate data available from humans for
an increased risk of a relatively rare form of cancer (nasopharyngeal
cancer), and a supporting mechanism, demonstrates the value and
strengths of the Monographs Programme," emphasized Dr Boyle. The
working group also found limited evidence for cancer of
the nasal cavity and paranasal sinuses and "strong but not
sufficient evidence" for leukaemia. The finding for
leukaemia reflects the epidemiologists’ finding of strong
evidence in human studies coupled with an inability to identify
a mechanism for induction of leukaemia, based on the data
available at this time. "By signalling the degree of evidence
for leukaemia and cancer of the nasal cavity and paranasal
sinuses, the working group identified areas where further
clarification through research is needed. This represents a
service to Public Health", Dr Boyle concluded.

Formaldehyde is produced
worldwide on a large scale. It is used mainly in the production
of resins that are used as adhesives and binders for wood
products, pulp, paper, glasswool and rockwool. Formaldehyde is
also used extensively in the production of plastics and coatings,
in textile finishing and in the manufacture of industrial
chemicals. It is used as a disinfectant and preservative (formalin)
in many applications.

Common sources of exposure include vehicle emissions, particle
boards and similar building materials, carpets, paints and
varnishes, foods and cooking, tobacco smoke, and the use of
formaldehyde as a disinfectant. Levels of formaldehyde in
outdoor air are generally low but higher levels can be found in
the indoor air of homes.

Occupational exposure to
formaldehyde occurs in a wide variety of occupations and
industries: for example, it is estimated that more than one
million workers are exposed to some degree across the European
Union. Short-term exposures to high levels have been reported
for embalmers, pathologists and paper workers. Lower levels have
usually been encountered during the manufacture of man-made
vitreous fibres, abrasives and rubber and in formaldehyde
production industries. A very wide range of exposure levels has
been observed in the production of resins and plastic products.
The development of resins that release less formaldehyde and
improved ventilation has resulted in decreased exposure levels
in many industrial settings in recent decades.

The working group also evaluated
two glycol ethers (2-butoxyethanol and 1-tert-butoxy-2-propanol)
and evaluated these as not classifiable as to their
carcinogenicity to humans, due to the inadequate level of
evidence in humans and limited evidence in experimental animals
available to the experts. Further research is needed on these
widely-used solvents.

The IARC Monographs
The IARC Monographs series publishes authoritative independent
assessments by international experts of the carcinogenic risks posed to
humans by a variety of agents, mixtures and exposures. Since its
inception in 1972, the series has reviewed more than 880 agents, and
IARC Monographs have become well-known for their thoroughness, accuracy
and integrity.
http://monographs.iarc.fr/. For details about evaluation criteria,
please link to
http://monographs.iarc.fr/ENG/Classification/index.php.